EFM Techniques Research Articles

Elaboration and investigation of formulated polymer composites as some potential anticorrosion coatings for brass surface in 3.5% NaCl solution: theoretical approaches

ABSTRACT Polymer composite derivatives [(TGEMM/MDA/0%, TGEMM/MDA/6%, TGP/MDA/0%, and TGP/MDA/6%)] were elaborated through using tetraglycidyl ether of methyl-α-D-mannopyranoside (TGEMM) and 2,3,4,5-tetraglycidyloxy pentanal (TGP) as matrices, methylene dianiline (MDA) as curing agent and glass system (1-x) (2Bi2O3 - B2O3) - x BaO (with x = 0% and 6%) as filler. Different composites prepared were investigated as some potential anticorrosive protection coatings for brass electrode in sodium chloride medium (3.5% NaCl). Polymer composite coatings were characterized using FTIR spectroscopy, SEM/EDS, EFM, PDP, and EIS techniques. The anticorrosive protection efficiencies increase with increasing charge incorporated in composites, in the following order: TGP/MDA/0% < TGEMM/MDA/0% < TGP/MDA/6% < TGEMM/MDA/6% and the later achieving a maximum of 90.67% (EFM), 95.45% (PDP), and 97.86% (EIS), respectively. SEM/EDS characterization suggests a smooth surface in the presence of composite derivatives, which is more significant in the presence of TGEMM/MDA/6%. DFT calculations and MD simulations confirm the data obtained by experimental study and offer insights into its structural properties.

(Invited) Combining Machine Learning, DFT, EFM, and Modeling to Design Nanodielectric Behavior

Polymer Nanodielectrics are class of materials with intriguing combinations of properties. Predicting and designing the properties, however, is complex due to the number of parameters controlling the properties. This makes it difficult to compare results across groups, validate models, and develop a design methodology. This presentation will share a recent approach to developing a data driven design methodology grounded in physics-based models and experimental calibration. We combine finite element modeling of dielectric constant and loss functions with a Monte Carlo multi-scale simulation of carrier hopping to predict break down strength. Filler dispersion, filler geometry, isotropy and interface properties are explicitly taken into to account to compute objective functions for ideal nanodielectric insulators. Further, we have used machine learning to develop an EFM technique for directly measuring the dielectric constant of the nanoscale interfacial region as critical input to our models. Ultimately, we calculate the Pareto frontier with respect to nanocomposite constitute properties and geometry to optimize properties.The finite element approach can be used to forward predict properties based on the properties of the interfacial region and filler dispersion, or as an inverse tool to calculate interface properties or develop optimized filler morphologies. The breakdown strength model critically depends on the energy distribution of trap states that inhibit space charge motion. We have developed an ab initio approach to determine the trap states at amorphous interfaces, and have used that to do a systematic analyses of trap distributions in composites with functionalized particle interfaces. The models all use 3D particle distributions based on 2D imaging (TEM) of the composites and publicly available tools for binarization and characterization of filler morphology. Finally, we use a design of experiment approach (Latin Hybercube Design) to sample the complete experimental design space, and using calibrated models and morphologies, create a data set spanning the full set of parameters. We use the data from the DOE to train a Gaussian Process metamodel and a genetic algorithm to determine which designs fulfill the design parameters. The talk will present several case studies as examples.The data for this work was accessed from a new data resource, MaterialsMine, using FAIR (Findable, Accessible, Interoperable, and Reusable) principles. MaterialsMine is an open source data repository, and resource. It includes unique visualization tools as well as modeling and characterization resources.

A temperature compensated biaxial eFM accelerometer in Epi-seal process

This paper reports on the implementation of a vacuum-encapsulated bi-axial resonant accelerometer utilizing the electrostatic frequency modulation (eFM) technique. A novel flexure structure is designed to enable fully-decoupled in-plane displacement of the proof-mass to minimize cross-axis sensitivity. A differential readout scheme leveraging pairs of high quality factor (>12k) free-free beam resonators mitigates the first-order nonlinearities due to temperature effects and unwanted response to proof-mass spurious modes. The fabricated device measures a scale factor of 45.8 Hz/g with negligible cross-axis sensitivity (<2 %). Furthermore, the smooth characteristics of temperature coefficients of frequency (TCf) of the resonators enable an accurate temperature sensor using the common-mode frequency of the resonator pair. Applying a temperature compensation scheme utilizing the common-mode frequency output and pre-characterized TCfs, the accelerometer demonstrates superior performance measuring a VRW of 5.8 μg/√Hz and BI of 5.7 μg with a scale factor stability of 0.38 % and zero-g-output variation of 8.3 mg over temperature range from –20 °C to 80 °C.

Graphene/h-BN heterostructures under pressure: From van der Waals to covalent

Scanning probe microscopy and ab initio calculations reveal modifications on the electronic and structural properties of graphene/h-BN heterostructures induced by compression. Using AFM and EFM techniques, with charge injection being made in the heterostructures at different pressures, the charge injection efficiency monotonically decreases with increasing pressure for monolayer-graphene (MLG)+BN heterostructures, indicative of a conductor-insulator electronic transition. Bilayer-graphene (BLG)+BN and trilayer-graphene (TLG)+BN heterostructures show a non-monotonic behavior of charge injection versus pressure, indicative of competing electronic structure modifications. First-principle calculations of these systems indicate a pressure-induced van der Waals-to-covalent interlayer transition, where such interlayer covalent binding, in the presence of water molecules, results in a disordered insulating structure for the MLG + BN case, while it leads to an ordered conducting structure for both BLG + BN and TLG + BN heterostructures. These opposing effects may have a strong influence on graphene/h-BN-based electronic devices and their physics under pressurized environments.

Controlling of mild-steel corrosion in acidic solution using environmentally friendly ionic liquid inhibitors: Effect of alkyl chain

In this study three environmentally friendly ionic liquids (ILs) namely: 1-Methyl-3-propylimidazolium iodide (MPIMI), 1-butyl-3-methylimidazolium iodide (BMIMI) and 1-hexyl-3-methylimidazolium iodide (HMIMI) were examined as inhibitors for suppressing mild-steel corrosion in 1 M HCl solution. PDP, EFM and EIS techniques were used to study the inhibition action on the metal surface. PDP study revealed that these ILs acted as mixed-type inhibitors due to their adsorption on the steel surface following Langmuir adsorption isotherm. The negative values obtained for Gibbs free energy supported the spontaneous physical adsorption of these inhibitors. Pronounced elevation in the inhibition efficiency was achieved with increasing the concentration of the ILs with maximum inhibitions of 93.1%, 87.8% and 80.4% using 5 × 10−3 M for HMIMI, BMIMI and MPIMI, respectively. To confirm the electrochemical results, the surface morphology of mild-steel was examined using AFM, SEM, and FT-IR analysis. The results confirmed the significance of the alkyl-chain length and the iodide anion present in the ILs on the inhibition mechanism. The results obtained from the different electrochemical and imaging techniques supported each other and strongly suggested that these eco-friendly compounds can be important for several industrial applications.

Pitting resistivity of Ni-based bulk metallic glasses in chloride solution

Resistance of new Ni70Cr21Si0.5B0.5P8C≤0.1Co≤1Fe≤1 and Ni72.65Cr7.3Si6.7B2.15C≤0.06Fe8.2Mo3 glassy alloys to pitting corrosion was studied in 0.25 M sodium nitrate solution, with or without addition of chloride ions, using EIS, CP and EFM techniques.

Inhibitive action and adsorption behavior of cefotaxime drug at copper/hydrochloric acid interface: electrochemical, surface and quantum chemical studies

The inhibitive action and adsorption behavior of cefotaxime drug on corrosion of copper in 0.1 mol L−1 HCl solutions was discussed using potentiodynamic polarization, EIS, EFM, SEM and EDX techniques.

Sweet Corrosion Inhibition on API 5L-B Pipeline Steel

Corrosion inhibition and adsorption behavior of two triazole derivatives on API 5L-B carbon steel in CO2-saturated 3.5% NaCl solutions was investigated using potentiodynamic polarization, EIS and EFM techniques. Specimen surfaces were characterized using SEM, EDX and XRD. Results show that the two compounds are mixed-type inhibitors and inhibition efficiency increases with increasing concentrations. Adsorption of the two compounds is a mixed between chemisorptions and physisorption and obeys Langmuir adsorption isotherm. Activation energy and thermodynamic parameters were calculated. Surface analyses confirm the formation of iron nitrides on the metal surface, which supports results obtained from previous techniques.

Corrosion inhibition effect and adsorption of aniline derivatives on QD36 steel surface in acidic solution

Inhibition of QD36 steel corrosion in 0.5 M HCl solution by aniline derivatives was studied using chemical (weight loss), potentiodynamic polarization and electrochemical frequency modulation measurements. The adsorption process of studied aniline derivatives on steel surface obeys the Langmuir adsorption isotherm. The values of activation energy (E*a), adsorption equilibrium constant (K ads), free energy of adsorption (ΔG ads ° , adsorption enthalpy (ΔH ads ° ) and adsorption entropy (ΔS ads ° )were calculated and discussed. Potentiodynamic polarization measurements showed that aniline derivatives are mixed-type inhibitors. The results obtained by EFM technique were shown to be in agreement with other chemical and electrochemical techniques. Scaning electron microscope (SEM) was used to study the surface morphology of the QD36 steel in 0.5 M HCl solution in the absence and presence of inhibitors. Further, theoretical calculations were carried out and relations between computed parameters and experimental inhibition efficiency were discussed.

Electrostatic tip-dielectric sample interaction in electrostatic force microscopy

Electric force microscopy is a local technique for measuring electrical properties of materials. The electrostatic force gradient measurements on dielectric samples are sensitive not only to the initial charge distribution in the sample but also to the charge induced by the conductive bias cantilever. Interpreting the contribution of each single effect on the charge distribution images is a challenge in the existing EFM technique. Here, a theoretical model is introduced to study the charge and induction effect on charged dielectric samples and commercial geometries for EFM tips. This model estimates the initial charge of the sample based on force gradient measurements. Gradient force results reproduce experimental measurements performed on electrets samples.

Sweet Corrosion Inhibition on API 5L-B Pipeline Steel

Corrosion inhibition and adsorption behavior of two triazole derivatives on API 5L-B carbon steel in CO2-saturated 3.5% NaCl solutions was investigated using potentiodynamic polarization, EIS, and EFM techniques. Specimen surfaces were characterized using SEM, EDX, and XRD. Results show that the two compounds are mixed-type inhibitors and inhibition efficiency increases with increasing concentrations. Adsorption of the two compounds chemisorption and obeys Langmuir adsorption isotherm. Activation energy and thermodynamic parameters were calculated. Surface analyses confirm the formation of iron nitrides on the metal surface which supports results obtained from previous techniques.

Investigation and in situ visualisation of interfacial interactions of thermophilic microorganisms with metal-sulphides in a simulated heap environment

This study sought to provide a better understanding of the dynamics of microbial-metal sulphide interfacial processes relevant to heap bioleaching. Attachment and subsequent biofilm formation by Metallosphaera hakonensis (M. hakonensis) on the surface of massive chalcopyrite and pyrite samples, as well as a low-grade chalcopyritic whole ore were investigated. The method made use of a biofilm reactor in which thin sections of mineral ore were mounted. Operating conditions in the reactor simulated those of a bioheap in terms of fluid-flow and mineralogy, where the low-grade chalcopyrite ore sections were used. Pure cultures of M. hakonensis were used to inoculate the reactors and the attachment and subsequent biofilm development visualised in situ after 2, 4 and 8 days using a combination of atomic force and epifluorescent microscopy (AFM–EFM) as well as confocal scanning laser microscopy (CSLM). This revealed insights into biofilm structure and architecture. The effect of varying temperature on the extent of attachment and biofilm development was also assessed after 4 days using three temperature regimes: room temperature (20±1°C), 45°C and 65°C. The density of the attached micro–colonies increased with an increase in time, indicative of an actively growing biofilm. The extent of surface coverage and proliferation of the biofilm was dependent on the temperature, with surface coverage being more extensive at 65°C, near the optimal temperature for growth. Preferential attachment and biofilm formation to sulphide minerals was observed, with increased surface coverage of pyrite mineral surfaces relative to chalcopyrite and low-grade ore. The AFM–EFM technique enhanced the level of detail at which site specific associations of microorganisms with mineral surfaces could be assessed. Spatial orientation and density of attached micro-colonies were noted.

Effect of Tryptophan on the corrosion behavior of low alloy steel in sulfamic acid

Sulfamic acid is widely used in various industrial acid cleaning applications. In the present work, the inhibition effect of Tryptophan (Tryp) on the corrosion of low alloy steel in sulfamic acid solutions at four different temperatures was studied. The investigations involved electrochemical methods (electrochemical impedance spectroscopy; EIS and the new technique electrochemical frequency modulation; EFM) as well as gravimetric measurements. The inhibition efficiency and the apparent activation energy have been calculated in the presence and in the absence of Tryp. It is most probable that the inhibition property of Tryp was due to the electrostatic adsorption of the protonated form of Tryp on the steel surface. Adsorption of the inhibitor molecule, onto the steel surface followed the Temkin adsorption isotherm. The thermodynamic parameters of adsorption were determined and discussed. All of the obtained data from the three techniques were in close agreement, which confirmed that EFM technique can be used efficiently for monitoring the corrosion inhibition under the studied conditions.

Erratum to: Evaluation of electrochemical frequency modulation as a new technique for monitoring corrosion and corrosion inhibition of carbon steel in perchloric acid using hydrazine carbodithioic acid derivatives

Electrochemical frequency modulation, EFM is a new technique for corrosion rate measurements. With the EFM technique, the corrosion rate and corrosion kinetic parameters can be obtained instantaneously without prior knowledge of Tafel slopes, which makes this method an ideal technique for application as a corrosion monitoring tool. Results obtained with the EFM technique were shown to be in agreement with chemical (weight loss) and electrochemical methods (Tafel extrapolation and electrochemical impedance spectroscopy, EIS) for corrosion rate measurements. New synthesized hydrazine carbodithioic acid derivatives namely, N′-furan-2-yl-methylene-hydrazine carbodithioic acid (A), N′-(4-dimethylamino-benzylidene)-hydrazine carbodithioic acid (B) and N′-(3-nitro-benzylidene)-hydrazine carbodithioic acid (C) were examined as corrosion inhibitors for carbon steel in 1 M perchloric acid solution. The results obtained from both chemical and electrochemical measurements show that these compounds suppressed both anodic and cathodic processes of carbon steel corrosion in 1 M HClO4 by adsorption on the electrode surface. The adsorption mode follows the Langmuir adsorption isotherm. The efficiency of the inhibitors increases in the order C > B > A.

220401 AFM電気力顕微鏡法を用いたCMP時の機械的研磨で生じる表面電位の評価(OS16 東京ブロック・山梨ブロック共同企画 機械工学が支援する微細加工技術(半導体・MEMS・NEMS)2(研磨プロセス),オーガナイズド・セッション)

220401 AFM電気力顕微鏡法を用いたCMP時の機械的研磨で生じる表面電位の評価(OS16 東京ブロック・山梨ブロック共同企画 機械工学が支援する微細加工技術(半導体・MEMS・NEMS)2(研磨プロセス),オーガナイズド・セッション)

Electroactive Nanorods and Nanorings Designed by Supramolecular Association of π‐Conjugated Oligomers

In investigations into the design and isolation of semiconducting nano-objects, the synthesis of a new bisureido pi-conjugated organogelator has been achieved. This oligo(phenylenethienylene) derivative was found to be capable of forming one-dimensional supramolecular assemblies, leading to the gelation of several solvents. Its self-assembling properties have been studied with different techniques (AFM, EFM, etc.). Nano-objects have successfully been fabricated from the pristine organogel under appropriate dilution conditions. In particular, nanorods and nanorings composed of the electroactive organogelator have been isolated and characterized. With additional support from an electrochemical study of the organogelator in solution, it has been demonstrated by the EFM technique that such nano-objects were capable of exhibiting charge transport properties, a requirement in the fabrication of nanoscale optoelectronic devices. It was observed that positive charges can be injected and delocalized all along an individual nano-object (nanorod and nanoring) over micrometers and, remarkably, that no charge was stored in the center of the nanoring. It was also observed that topographic constructions in the nanostructures prevent transport and delocalization. The same experiments were performed with a negative bias (i.e., electron injection), but no charge delocalization was observed. These results could be correlated with the nature of 1, which is a good electron-donor, so it can easily be oxidized, but can be reduced only with difficulty.

Electrochemical frequency modulation as a new technique for monitoring corrosion inhibition of iron in acid media by new thiourea derivative

The electrochemical frequency modulation EFM technique provides a new tool for electrochemical corrosion monitoring. EFM is a non-destructive technique as electrochemical impedance spectroscopy (EIS). EFM technique was used in comparison with the traditional dc and ac techniques. Results obtained by EFM technique were shown to be in agreement with other electrochemical techniques. With EFM technique, a corrosion rate can be obtained instantaneously in very short time which makes this technique ideal in online corrosion monitoring. New synthesized thiourea derivative named 1,3-diarylidenethiourea (DAT) was examined as a new corrosion inhibitor for iron in 1 M hydrochloric acid solution.

Measurement of Surface Topography, Packing Density, and Surface Charge Distribution of an Electrostatically Deposited Powder Layer by Image Analysis of Fluorescent Latex Spheres

A novel method of nonintrusive measurement of surface profile, packing density, and surface charge distributions of a powder layer deposited on a substrate is reported. The method employs the deposition of electrostatically charged monodispersed fluorescent latex spheres (FLS), approximately 2 m in diameter, on the surface of: (1) the substrate before deposition, (2) the powder layer after deposition, and (3) the film formed by curing the powder layer. The surface topography in all cases was mapped using an epi-fluorescent microscope with a vertical resolution of - 2 m in the z axis and - 10 m in the x and y axes. An area of 1 cm 2 1 cm is scanned in 1 mm segments, providing approximately 100 data points per cm 2 for the surface topography. For each measurement of surface topography, the substrate was positioned on the microscope stage in a manner such that the reference points (x, y, and z) remained the same for all measurements of the substrate. The surface profiles, with respect to the same reference points, were plotted using Origin 6.0 software for 3D presentation of the topography. The method was also applied to map the surface charge density distribution of electrostatically charged surfaces. The FLS imaging method provides a new tool for examination of surface profiles, packing density, and charge distribution of powder layers on a microscopic scale not provided by optical or atomic force/electrostatic force microscopy (AFM/EFM). While AFM and EFM are very effective in providing similar information with nanometer resolution, they cannot be directly applied on a larger macroscopic scale to study powder layers and for a larger surface area (up to 1 cm 2 or greater) involving deposited particles in the range of 1-50 m in diameter. For AFM, the range in the z-axis is limited to - 3 m and the x-y scan area is limited to 100 m 2 100 m. The FLS method has a much wider range but it is operated manually; an automated scanning process is required for rapid measurement. A comparison of the FLS and EFM techniques as they apply to analyzing charge distribution on coal surfaces is presented.